1. Field
The following description relates to a technique to offer high-speed link protection switching from an erroneous link to a standby link in a passive optical network (PON) into which wavelength division multiplexing (WDM) and time division multiple access (TDMA) are combined.
2. Description of the Related Art
Passive optical networks (PONs) are largely classified into a time division multiplexing (TDM)-PON and a wavelength division multiplexing (WDM)-PON. Examples of the WDM-PON include an Ethernet PON (EPON) and a Gigabit PON (GPON). The WDM-PON allows multiple subscribers to share bandwidth in time domains. Accordingly, the more subscribers, the less the bandwidth available. In order to address this problem, the TDM-PON uses N times more optical fibers and equipment than the WDM-PON. The WDM-PON uses different wavelengths for a single optical fiber, and allocates the different wavelengths to each subscriber, thereby addressing the bandwidth problem of the TDM-PON. However, since there are not yet many services that use such broad bandwidth, the WDM-PON may suffer from low efficiency of bandwidth utilization.
A WDM-TDM PON, which is also referred to as a hybrid PON, is a combination of the WDM-PON and the TDM-PON and offers the advantages of both the WDM-PON and the TDM-PON. More specifically, the WDM-TDM PON integrates a typical TDM-PON backbone relay network with a WDM-PON technology, and provides various advantages, such as 3 times longer transmission distances, 2 times higher split ratios, and 32 times larger link capacity, compared to a typical TDM-PON. However, such a long transmission distance and concentrated link capacity may increase the probability of link malfunction, and may require protection switching.
The WDM-TDM PON uses and is highly dependent on long optical fibers. Accordingly, a technique is needed to perform high-speed switching between optical fibers.